The invention relates to a pivot bearing for two connecting rods in at least one piston of an internal combustion engine comprising two crankshafts, which are driven by way of the piston and the connecting rods.
A pivot bearing for a piston of an internal combustion engine is known from EP 2 426 336 A2, which is designed to accommodate two connecting rods. The connecting rods of the piston cooperate with two crankshafts of the internal combustion engine and are disposed so as to be relatively movable by way of connecting rod eyes, mediated by connecting rod pins inserted into boreholes of the eyes. An intermediate space for the connecting rod eyes is provided between the connecting rod bearings. This pivot bearing is used to compensate for the system-related asymmetry during rotation of the two crankshafts.
JP 61-149745 relates to an internal combustion engine having a piston. The piston is connected to two crankshafts by way of two connecting rods. The connecting rods are operatively connected to connecting rod eyes having a wrist pin-like bearing pin, which is accommodated in boreholes of spaced, cylindrical bearing disks. The bearing disks, in turn, are inserted into boreholes of the piston in such a way that these are seated against axial stops in the boreholes of the piston. Radial retaining rings are used to axially fix the bearing disks and the bearing pin.
It is the object of the invention to design a pivot bearing for a piston of an internal combustion engine which has a high load-bearing capacity, yet a relatively light weight and which accommodates two connecting rods in an articulated manner, wherein the piston and the connecting rods drive two crankshafts. In doing so, however, the pivot bearing is also to be improved with respect to strength and wear.
This and other objects of the invention are achieved by a pivot bearing for two connecting rods in at least one piston of an internal combustion engine comprising two crankshafts, which are driven by way of the piston and the connecting rods, with the pivot bearing being accommodated in piston boreholes of the piston and having bolt boreholes for mounting connecting rod bolts for connecting rod ends of the connecting rods. The pivot bearing comprises radial bearing regions that are provided with the bolt boreholes and that are disposed on either side of a center longitudinal axis of the piston and delimit the connecting rod ends, forming an intermediate space. The bearing regions of the pivot bearing are designed as cylinder bodies having a crucible-like cross-section, of which each cylinder body has a base wall and a bearing ring jacket. The base walls of the two cylinder bodies extend at a distance from each other, and the bearing ring jackets surrounding the base walls are guided away from the base walls in opposite directions. One or more connecting supports run between the base walls. The bearing ring jackets cooperate with the piston boreholes in a rotatably movable manner. The base walls are connected to bearing bushings which are oriented in the axial direction of the pivot bearing and into which the bolt boreholes are incorporated. The pivot bearing is made of a material which brings about a targeted low-weight construction of the pivot bearing, while offering high strength and low wear.
The advantages that are primarily achieved with the invention can be seen in that the pivot bearing of the piston, which drives two crankshafts of the internal combustion engine mediated by two connecting rods, represents a lightweight component in the crank mechanism of this internal combustion engine causing lower forces of inertia due to the structural design and material selection. The design and material selection positively impact the dynamic engine properties and mechanical stress in the crank mechanism. The two crucible-shaped cylinder bodies with the bearing ring jackets thereof, base walls and bearing walls form exemplary components that are easy to implement. Also emphasized in this context shall be the connection of the two cylinder bodies via the connecting supports, which as a result of an appropriate design allow the necessary stability to be imparted under the stresses that occur by deliberately using lightweight construction measures. It is advantageous if the pivot bearing is made of a material that brings about a targeted low-weight construction of the pivot bearing while offering high strength and low wear. Excellently suited for this purpose is cast steel for components that have a high load-bearing capacity, statically and dynamically, and are subjected to especially high wear, but also an ultra-high carbon (UHC) lightweight steel.
The solution is that three connecting supports are provided between the base walls of the cylinder bodies, of which two connecting supports are provided in the direction of the piston crown of the piston at a distance from the connecting rod eye plane intersecting the centers of the connecting rod bolts of the connecting rod ends on the one hand, and from the center longitudinal axis of the piston on the other hand. The third connecting support, in the direction of the crankshafts, is located spaced from the connecting rod end plane of the center longitudinal axis of the piston.
The installation of the connecting rods is facilitated in that, originating from the first ring section of the cylinder bodies, which is directed to the piston crown to the second, opposing ring section of the cylinder bodies, which is directed toward the crankshafts, the base walls of the cylinder bodies diverge in a V-shaped manner so as to form the intermediate space for the connecting rod ends in a defined manner. The component is optimized when the bearing bushings protrude at a defined distance beyond the radial delimiting planes of the bearing jackets, and also when each bearing ring jacket on an inside in the region of the bearing bushings is provided with the first local thickened sections and is located spaced from the connecting rod end plane between the first thickened sections and the bolt boreholes of the bearing bushings. Moreover, the bearing bushings comprise second thickened sections in the region that faces the crankshafts.
The technical design sets standards, wherein, originating from the inside of the first ring section, one or more reinforcing ribs are provided in the direction of the bearing bushings. This is supported in that, on the one hand, at least one reinforcing rib in the center longitudinal axis of the piston runs radially between the inside and a transverse web that connects the bearing bushings and is located on the connecting rod end plane, and on the other hand, that multiple further ribs combine the inside with the bearing bushing in a secant-like manner.
Finally, another factor in the optimization of the pivot bearing is that the base walls between the connecting rod end plane and the second ring section have one or more through-passages so as to reduce the weight.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of one or more preferred embodiments when considered in conjunction with the accompanying drawings.